1. Field of the Invention
The present invention relates to a method of when carrying out sound communication between IP telephone gateway apparatuses connected to an IP network and a telephone network, between IP telephone terminals connected to an IP terminal, or the IP telephone terminal and the IP telephone gateway apparatus, requesting a router apparatus, for which a gate keeper apparatus can secure or release a band width, to secure and release a communication band width used in the communication between the above-mentioned apparatuses.
2. Description of the Related Art
In a conventional IP telephone connection protocol, a band required for the communication was secured or released along with origination or termination of a call. For example, in ITU-T H. 323, an IP telephone gateway apparatus, in originating call connection, in a sequence of an RAS (Registration, Admission & Status) protocol, informs a gate keeper of a communication band required for a call through an ARQ message, and in termination of a call, likewise, informs the gate keeper of the release of the communication band used in a call through a DRQ message. The gate keeper which has received the request therefrom informs the router apparatus of the security or release of the communication band. Then, the gate keeper, depending on whether or not the necessary band can be secured, sends as a reply in the form of an ACF message a connection permission to an IP telephone gateway apparatus, or sends as a reply in the form of an ARJ message a connection rejection to the IP telephone gateway apparatus.
In a conventional method of securing and releasing a band, a router which can secure or release a band width is requested to secure or release the band width in accordance with a protocol such as an SNMP (RFC1157), an RSVP (RFC2205) or a COPS (RFC2748). For example, in the RSVP, router apparatuses on a communication path actually used in communication are successively informed of a request to secure a band through a path message. Then, the communication only becomes possible in the desired communication band at a time point when the setting has been completed in all of the router apparatuses on the communication path and all of the router apparatuses have received an Resv message.
The router apparatus changes the priority of the relay processing of a relay packet in accordance with the request reported thereto by the above-mentioned various kinds of methods to secure or release the band.
In accordance with the general technique in the router apparatus, a packet relay processing queue for the general relay packet processing and a queue for the priority relay packet queue are prepared in the router apparatus and the packet of the queue for the priority relay packet is preferentially processed to secure the band. In addition, a priority relay packet table used to judge the packet to be put into the queue for the priority relay packet processing is prepared in the router apparatus. When a request to secure the band including at least a transmission source address and a transmission destination address has been made, this request is registered in the above-mentioned priority relay packet table. Thereafter, when having received a packet, a pair of transmission source address and transmission destination address of the packet is compared with the contents of the above-mentioned table to judge whether or not the matching is obtained therebetween. If it is judged that the matching is obtained therebetween, then the packet of interest is added to the last of the queue for the priority relay packet processing. On the other hand, if it is judged that the matching is not obtained therebetween, the packet of interest is added to the last of the queue for the general relay packet processing. With respect to the transmission of the packet, if the queuing is present for the queue for the priority relay packet processing, then the packet in the queue is preferentially transmitted, and otherwise, the packet in the queue for the general relay packet processing is transmitted.
In the conventional combination of the IP telephone connection protocol and the method of securing and releasing a band, the security request and the release request are made with the start and end of a session corresponding to one call as a turning point. When the number of lines accommodated in the IP telephone gateway apparatus is large, if that method is adopted, then there arises the problem that a ratio of occupation of the traffic due to the communication of the security request and the release request in the network between the gate keeper apparatus and the router apparatus become large and hence the number of bands which can be used in the sound communication is reduced.
In addition, a period of time ranging from the security request up to the actual security and a period of time ranging from the release request up to the actual release are each on the order of several seconds in many cases. For this reason, if that method is applied to the environment, such as the IP telephone, in which the origination and termination of calls are frequently generated, then there arises the problem that a processing amount in the router apparatus is increased, and hence the processing for securing and releasing a band is not enough to follow the processing amount in the router. As a result, it is impossible to secure the necessary communication band until the sound signal has been started to be relaid, and hence there is the possibility that the quality of the communication ranging from the call origination up to the actual security of a band is degraded.
In addition, in a method of securing fixedly previously a band, it is possible to avoid the influence of the processing time required for the security or the release in the router and also the possibility that the communication quality in originating a call may be degraded is cancelled. However, in the IP telephones, similarly to general telephones, a call amount undergoes the daily change, the weakly change and the yearly change. Therefore, if a call amount able to cope with the busy term is secured, then the number of useless bands is increased in the free term. As a result, there arises the problem that the utilization efficiency is poor.